std.random.randomCover and randomSample should warn that struct RNGs are copied (original is not updated)

[dlangBugzillaToGithub]

n8sh.secondary reported this on 2018-08-14T11:03:07Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=19168

CC List

• greensunny12

Description

The behavior is described in https://issues.dlang.org/show_bug.cgi?id=7067. Since the `rng` parameter is `auto ref` this behavior is not obvious merely from the function signature, so at the very least this quirk should be mentioned in the documentation.

[dlangBugzillaToGithub]

greensunny12 commented on 2018-08-15T13:22:08Z

Better ways:

- split in two overloads and deprecate the by value one
- fix random ranges in general by making them non-copyable (like suggested in #7067)

However, the latter is a lot of work and it might be easier to just submit a version of mir.random as std.experimental.random and to fully replace std.random (there has been some talk about doing this, but it never materialized.)